This invention concerns improvements in and relating to handling molten materials, particularly, but not exclusively, in relation to controlling the flow of molten metal from a tundish.
Casting operations generally employ a tundish to act as a reservoir of molten metal between the ladle and the mould. The ladle is used to convey molten metal from a melting location to the casting location. The mould is used to control the profile of the solidifying metal during casting.
To control the flow of metal from a tundish it is necessary to block and open an outlet in the tundish, in a controlled manner. In general this is achieved using a stopper element in the molten metal which cooperates with the outlet to seal it, the stopper being supported by a stopper guide which is moved up and down using an actuator.
The stopper is frequently supported at a considerable distance away from the portion of the stopper guide moved by the actuator. As a consequence of this problems in supporting the stopper in the correct alignment and with reasonable levels of friction exist. Prior art systems are prone to jamming and/or friction levels which give rise to uneven movement of the stopper, or excessive clearance can lead to misalignment. These problems all give rise to poor control of the flow from the tundish, as well as increasing the mechanical loading on the actuator system.
The present invention aims to provide an improved stopper gear mechanism in which the stopper movement and positioning is controlled with great precision and the mechanical loads on the stopper gear and actuator are reduced.
According to a first aspect of the present invention we provide apparatus for controlling the flow of material, such as molten metal, from a container, the apparatus comprising a closing element for the outlet from the container, a support system for the first element, an actuator system for moving the support system and first element, a fixed support frame for mounting the support system and first element, and a bearing system between the fixed support framework and the support system to facilitate movement of the support system relative to the fixed support framework, wherein the bearing system comprises one or more contact surfaces between a component of the support framework and a component of the support system, at least one of the components providing a contacting surface capable of rotation.
Preferably the bearing system facilitates reciprocating movement of this support system relative to the fixed support framework. Reciprocating movement along a vertical axis is preferred in this regard.
Preferably the contact surface(s) provided by one of the support framework or support system is a flat surface(s) The flat surface(s) may be provided by the support framework, preferably one provided by the support system, more preferably by the support shaft of the support system and most preferably by a face of a square cross-section part of the support shaft.
The contact surface capable of rotation may be provided by the support system, or more preferably by the fixed support framework. Preferably the rotatable contacting surface is provided by a unit mounted on the fixed support framework.
Preferably the unit comprises a mount, such as a shaft, providing rotation facilitating retention of the rotatable contact surface and attached to the fixed support framework. Preferably the rotation facilitating retention is provided by an axle engaging the element defining the rotatable contacting surface. Preferably the element is a cam or cam follower. The cam followers preferably have eccentric shafts.
Preferably at least two opposing contact surfaces between a component of the support framework and a component of the support system are provided. More preferably two sets of contact surfaces, in opposition to one another, between a component of the support framework and a component of support system are provided. Preferably the first set of opposing contact surfaces is offset by an angle of 90xc2x0 relative to the second set of contact surfaces. Preferably the axis of rotation for the first and/or second set of contact surfaces are provided in a common plane, most preferably a horizontal plane, and ideally a plane perpendicular to the component of the support or support framework in question. Two or more such groups of contact surfaces may be provided. Preferably one such set of contact surfaces are provided on an upper portion of the support system and a second set is provided on a lower portion of the support system.
Preferably the molten metal flows from the container to a casting or moulding operation. Preferably the molten metal is supplied to the container by a ladle. The container is preferably a tundish.
Preferably the first closing element comprises a stopper rod. Preferably the stopper rod is provided on a substantial vertical axis within the container. Preferably the end of the stopper rod is configured to cooperate in a sealing manner with the outlet from the container.
Preferably the outlet from the container is provided in the base of the container. Preferably the mouth of the outlet cooperates with the profile of the end of the stopper rod to give closure. The outlet may have rounded edges, at its internal periphery.
Preferably the support system comprises a laterally extending, most preferably horizontally extending, element. The element may be a bar.
Preferably the support system comprises, or further comprises, a substantially vertically aligned support shaft. Preferably the support shaft is received in the bearing system. Preferably the support shaft provides a mounting for the laterally extending element.
The support system may include one or more portions rotatably mounted relative to one another. For instance a support shaft, received in the bearing system may be provided, two or more portions of the support shaft being adapted to rotate relative to one another. Rotation may be facilitated by bushes. Preferably rotation occurs about the longitudinal axis of the shaft.
The support shaft may comprise one or more portions providing a contact surface of the bearing system, longitudinally spaced from one another on the shaft, rotation movement of the portions relative to one another being facilitating.
The support system may comprise, or preferably further comprise, an element linking the support shaft to the actuator. A horizontally extending element connected to the bottom of the support shaft is preferred in this regard.
The actuator system may comprise a reciprocating mover, for instance an hydraulic piston. Preferably the actuator reciprocates along a substantially vertically aligned axis.
Preferably the fixed support framework mounts the support system, via the bearing system, on the container. Preferably the support system is provided with a mounting on the side of the container.
According to a second aspect of the invention we provide means for providing a controlled supply of molten metal, the means comprising a container, adapted to receive molten metal in use, the container having an outlet, the outlet cooperating with the closing element of a control apparatus of the first aspect of the present invention.
The second aspect of the invention may include any of the means, options, possibilities and components set out in the first aspect of the invention and/or elsewhere in this document.
According to a third aspect of the present invention we provide a method for controlling the flow of molten metal from a container, the method comprising the steps of providing a volume of molten metal in the container, moving an actuator from a first position to a second position, the change in position of the actuator moving a support system relative to a fixed support framework by rotating a contact surface in the bearing system between the support system and the fixed support framework, the contact surfaces of the bearing system being defined between a component of the support system and the component of the fixed support framework, the movement of the support system moving a closing element for the outlet from the container, movement of the closing element away from the outlet facilitating flow of molten metal out of the outlet, movement of the closing element into contact with the outlet from the container preventing the flow of molten metal from the container.
Preferably movement of the actuator downward moves the closing element downward. Preferably movement of the actuator upward causes movement of the closing element upward.
The components, options, features, possibilities and steps of this method may further include details, features and possibilities set out elsewhere in this document.